The present invention relates generally to training equipment for pilots and more particularly to improved instrument flight training glasses.
Instrument flight training requires that the vision of the student pilot be restricted. That is, the student pilot's vision must be restricted to the instrument panel within the cockpit.
An effective pair of instrument flight training glasses is shown in U.S. Pat. No. 4,152,846 ("the Witt patent"), shown the teachings thereof are incorporated herein by reference. The Witt patent discloses a bistable voltage-controlled lens having a first transparent state and a second opaque, non-transparent state. The lens, a liquid crystal, includes a normally permanent sight-restricting upper portion and the voltage-controlled portion therebelow. The voltage-controlled portion extends the entire width of the lens.
The state of the bi-focal voltage-controlled lens is controlled by a position sensor which includes an ambient photocell and a directional photocell. As the student pilot raises his head in an attempt to look through the windshield, the position sensor responds and opaques the lower voltage-controlled lens portion. More particularly, as the head is raised from the instrument panel to the windshield, or when any outside viewing is attempted, the directional photocell in conjunction with the ambient photocell senses an increase in light, and the position sensor responsively switches the lens from the transparent state to the opaque state.